The invention relates to a camera and electronic flash combination, and more particularly, to such a combinatorial assembly in which an electronic flash capable of automatically controlling the flashlight illumination is mounted on a camera having an electrical shutter of non-memory, TTL photometry type to permit an efficient signal delivery between the both units.
When an electronic flash capable of automatically controlling the flashlight illumination is mounted on a camera having an electrical shutter of non-memory, TTL photometry type, a number of control schemes are possible depending on whether the control of the flashlight illumination from the electronic flash is controlled by a signal derived from a photometric light receiving element disposed within the camera and which is responsive to reflective light from an object being photographed and which is used for controlling the electrical shutter, or by a signal from another photometric, light receiving element which is disposed within the electronic flash. In one instance, the control of the flashlight illumination is governed by one of these signals whichever occurs first. However, the user then is unable to know which signal controlled the flashlight illumination. If he wanted to take a picture according to the TTL photometry technique, the electronic flash may be controlled in response to a control signal which is produced from the light receiving element contained therein, thus defeating the very purpose of a single lens reflex camera having TTL photometry, light receiving element.
In another instance, there is provided a camera in which the TTL photometry is automatically established whenever an electronic flash is mounted thereon. This arrangement suffers from the inability to control the flashlight illumination in response to an output from a light receiving element which is provided on the part of the electronic flash.
There is also known a combination of a camera and an electronic flash, each of which is provided with its respective manual switching mechanism which enables the control of the flashlight illumination in response to an output from a light receiving element associated with the respective unit. In this instance, both switching mechanisms must be individually operated to a desired position. In the event the camera is of the type which can be switched into a manual operation and in which the light receiving element associated with the camera can be disconnected from the circuit within the camera, the normal control of the flashlight illumination is lost if the selection made on the part of the camera does not coincide with that on the part of the electronic flash. Moreover, it is understood that the coincidence of such selections is liable to be forgotten, giving rise to an inadvertent use.
For a combination of an electronic flash having the capability to control its flashlight illumination automatically and a camera having an electrical shutter of the TTL photometry type, the shutter can be closed in a number of ways, depending on the selection of a particular signal to which it responds. In one arrangement, an exposure period under the flashlight illumination is previously established within the camera, and synchro contacts are adapted to be closed at the end of running of a first shutter blind and at the beginning of running of a second shutter blind. In this instance, the shutter may be closed if the electronic flash fails to produce an illumination in the event the power supply associated with the electronic flash is not properly connected or the charging capacitor thereof is not properly charged, resulting in a failure to take a picture.
In another arrangement, a fixed shutter period is established when an electronic flash is mounted or when the charging is complete. In this instance, the absence of the detection of illumination from the electronic flash allows the shutter to be closed if the illumination circuit fails to operate, resulting in a failure to take a picture. Because the photometric function provided on the part of the camera is not activated, the exposure is solely determined on the part of the electronic flash, so that an overexposure may result for an object which is under bright illumination, thus destroying the very advantage of TTL photometry camera.
Finally, when an electronic flash having the capability to control its flashlight illumination automatically is used in combination with a camera having an electrical shutter of non-memory, TTL photometry type, it is desirable to provide a variety of functions including closing of the shutter, the display of the completion of a charging operation, luminescent display, and the display of the completion of flashlight illumination. However, in order to enable all of these functions, an increased number of electrical connections or contacts between the both units results.